If you have ever hit send in Klaviyo whenever the email happened to be finished, you are not the only one. Klaviyo send time is one of those settings that looks simple until you open the scheduler and realize there are a few different ways to decide when a campaign actually goes out. Most brands use one of them, if any.

This is the practical version: fixed send time, Smart Send Time, Personalized Send Time, and the checkbox I want you to check before you schedule.

Why your Klaviyo send time is probably a guess

A weekly newsletter someone might read in pieces is a different timing problem than a one-time discount. A D2C audience often engages more in the evening. Parents may not open their inbox until after bedtime. And if you sell something tied to daylight, like blackout curtains or melatonin, sunset is not a cute detail. It is context.

Klaviyo gives you more control over this than most people use. Here is how the main options actually work.

#1 Fixed send time is the Klaviyo baseline

Fixed send time is the option everybody already knows. You pick a time. Everyone gets the email around then, either in your account’s timezone or in each person’s local time. Nothing fancy, and it works fine for a lot of campaigns.

It is also the right place to start if you do not have enough list data for the automated options below. A deliberate fixed time is already better than sending the moment the draft is done.

#2 How Smart Send Time works in Klaviyo

Smart Send Time is Klaviyo’s older, audience-level tool. It looks for one strong time for the whole audience, not a different time for every person.

To run the exploratory and focused tests, you need a campaign audience of at least 12,000 people, and an email plan that can send to that many profiles. Under that line, the option will not be available. Klaviyo’s Smart Send Time guide spells out the thresholds. ⁠

Exploratory send, then a focused send

The first phase is an exploratory send. Over 24 hours, Klaviyo assigns people different times in their own local time, just to see when this audience actually engages. Depending on list size, you may need more than one exploratory send before the model has enough data.

After that, Klaviyo moves to a focused send. It splits recipients into three groups around the time that looked strongest, one at the candidate time and two in a two-hour window on either side, still in each person’s local time. That phase confirms and refines the result as behavior changes.

Once an optimal time is established, you can keep sending there. Optimal send time can be used for audiences of any size. The 12,000 minimum is for the testing phases, not for every later send.

Do not use Smart Send Time for anything time-sensitive. A flash sale or a deadline email needs people to receive it in a coordinated window. Smart Send Time is built to find the best moment for engagement, not to synchronize everyone at once.

If you are under 12,000 recipients

You are not stuck guessing. You just have to test it yourself.

In the campaign builder, use the option to test send times. Keep everything else the same: same content, same subject line, and only the time changes. Then you know the difference in performance is about timing, not about the email.

If you have no starting point, evening is a reasonable first guess to test against. Treat it as a guess, not a rule.

What should drive a Klaviyo send time decision

“When do people open email in general” is the wrong question. A few specifics matter more.

• What kind of email it is. A weekly newsletter can land earlier in the day and still get read. A one-time discount needs enough time for someone to see it, click, and buy before the urgency fades, and not so much time that they forget it.
• Who you are sending to. A D2C audience often engages more in the evening. Parents may not sit down with their inbox until after bedtime. Your customer’s actual day beats a generic benchmark.
• Where they live, not just the time zone. Sunrise and sunset can matter. If you sell blackout curtains or melatonin, when it gets dark in someone’s part of the world is relevant context.
• How often you already send. If you are just getting started with a smaller list, Klaviyo’s general recommendation is to start around one campaign a week and build from there, usually with a mix of one newsletter-style send and a couple of more sales-focused sends each month. Cadence shapes timing. Sending too often, at the wrong times, is how people tune out.

If you want a related look at what happens after someone opts in, I subscribed to 362 real ecommerce brands and nearly half never sent a welcome email at all. The breakdown and the audit checklist are free: joyjoya.com/frontdoor.

#3 Personalized Send Time works one person at a time

Personalized Send Time is the newer option, and it does not look for one best time for everyone. It predicts a time for each recipient from their own engagement history and from similar profiles, then sends inside a window you choose.

It is not on every account. You need a Marketing Analytics or Advanced Klaviyo Data Platform package. If you do not see it, that is the likely reason. It currently works for campaigns, not flows, and you have to schedule at least a day ahead. Same-day sending is not available. Klaviyo also says not to use it for time-sensitive content, for the same reason as Smart Send Time: people will not all receive it at the same clock time. Klaviyo’s Personalized Send Time documentation covers the current limits.⁠

Klaviyo has shared testing where one brand saw over a 10% lift in placed order rate after switching to it for non-urgent campaigns. That is one result, not a promise. If you are just starting and do not have a test yet, evening or late morning are both reasonable places to begin. The test is still how you find out what is true for your list.

The Klaviyo checkbox that can shrink campaign reach

When you schedule a campaign, there is a toggle called Determine recipients at send time. In my opinion, this should be checked whenever Klaviyo lets you use it.

Here is what it does. Checked, Klaviyo takes a fresh snapshot of your list or segment close to send time, instead of freezing the audience the moment you hit schedule. Unchecked, the audience locks when you schedule. Someone who joins an hour before the send, and who would have qualified, simply will not get it. Not because anything is broken. Because the segment was already frozen.

I have seen this happen. It is usually a small handful of people, and it is still real reach missed for one unchecked box. Klaviyo’s schedule and send options explain the snapshot behavior.

One limit, so you do not hunt for a box that will not appear: if you send by each recipient’s local time, Klaviyo does not let you also determine recipients at send time. In that setup, no new recipients are added after you schedule. The checkbox is the habit to build when you are sending in one specific timezone.

Pick a Klaviyo send time on purpose

Most brands are underusing what Klaviyo already gives them. You do not need Personalized Send Time to see a difference. Being deliberate about fixed send time versus Smart Send Time, and not accidentally freezing your audience, is already a meaningful upgrade from hitting send whenever the email is done.

If you want help building email and SMS that actually drives sales, start at joyjoya.com.